Determination of the nature of the transduction, encoding, processing, and perception of complex biologically significant signals is our major objective. An interdisciplinary approach to such a problem is essential. Investigators trained in different disciplines combine their talents in direct cooperation and form three closely integrated and collaborative projects to define and analyze the major events from acoustic activation of inner ear receptors to perception. The objectives are approached by experiments on: (1) biochemical and immunological characteristics of auditory receptor cells that determine the molecular events involved in transduction; (2) electrophysiological features of hair cells and central auditory cells from cochlear nucleus to auditory cortex that determine encoding and processing; and (3) behavioral responses that reflect perceptual capacities of the auditory system for the identification, discrimination, and classification of these complex signals. These projects are designed to yield information on the reception, processing and perception of complex signals at three levels of analysis. Data from each level of analysis impacts on the definition of experimental questions in the other projects. The result will be a comprehensive view of the auditory system characteristics that underlie perception of speech. The research group including specialized personnel in biochemistry, immunology, neuropharmacology, electrophysiology, psychoacoustics, bioengineering, and animal behavior provides a critical mass for the conceptualization and design of these studies. The Hearing Institute as a facility with appropriate laboratories, technical and support capabilities provides the ideal means for conduct of these studies. This program will represent the core focus of this institute and its professional personnel. This focus on this fundamental problem of audition is timely. The program represents a new direction for this group and is unique to the field. Clear and important clinical relevance of this program lies in the specification and definition of unique events in auditory processing of complex signals, which will lead to improved designs for speech processors for cochlear prostheses and hearing aids, and a clearer understanding of the basis and course of speech discrimination deficits with sensorineural hearing loss.